Thousands of people who fled fighting in South Sudan's Lote state, have resorted to eating leaves and roots as they battle hunger, a Catholic priest in the East Africa country has said.

"Some people are in the bush depending on leaves and roots. The situation in Raga is really very bad. People are really suffering," Father Richard Batista Engliz said.

The situation in Raga is really very bad. People are really suffering

Thousands of people are sheltered at the Catholic Church in Raga since last Friday when fighting broke out between government troops and fighters loyal to former vice president, Riek Machar in nearby villages.

"Two thousand five hundred people are now sheltered at church buildings and schools. Apart from occupying church buildings, others are at Comboni girls and boys' secondary schools, which belong to the church," Engliz said.

He said the church has been overwhelmed by the big number of people seeking safety and is in urgent need of food medical supplies.

Enliz said the church had run out of drugs and "the health situation is deteriorating", adding that "medical staff to attend to the big number of people" is needed.

He said UN agencies and NGOs have assessed the situation and promised to provide assistance soon.

Fighting broke out in South Sudan's capital, Juba, in June after an already difficult relationship between President Salva Kiir and his then deputy, Machar deteriorated.

Following Kiir's sacking of Machar, fighting has erupted in other parts of the country between government troops and fighters loyal to the axed deputy, which has led to thousands of people being displaced.